In downlink transmission of a long term evolution (Long Term Evolution, LTE) Release 8/9/10 communication system, an evolved base station (Evolved Node B, eNB) sends a physical downlink shared channel (Physical Downlink Shared Channel, PDSCH) and a corresponding physical downlink control channel (Physical Downlink Control Channel, PDCCH) for each scheduled user equipment (User Equipment, UE) according to a scheduling result, where the PDSCH bears data sent to the scheduled user equipment UE by the eNB, and the PDCCH bears scheduling information of its corresponding PDSCH. The scheduling information is mainly used for indicating transmission format information of its corresponding PDSCH, which includes resource allocation, the size of a transmission block, a modulation and coding manner, a transmission rank and pre-coding matrix information, and so on. The PDCCH and PDSCH are multiplexed into one subframe through a time-division multiplexing. For a general cyclic prefix, each subframe includes two slots (slot), there are seven orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM) symbols in each slot, where the PDCCH is transmitted in the first n (n=1, 2, 3, 4) OFDM symbols of the first slot, n is dynamic and variable and the remaining OFDM symbols are used for transmitting the PDSCH.
In one subframe, PDCCHs of all scheduled user equipments UEs are multiplexed together and then sent in a PDCCH region. Each PDCCH consists of 1/2/4/8 control channel elements (Control Channel Element, CCE), where the number of CCEs consisted in each PDCCH is determined by the size of the PDCCH and a channel of the user equipment corresponding to the PDCCH. The number of CCEs consisted in each PDCCH of the user equipment may be different.
Due to introduction of technologies such as multiple input multiple output (Multiple Input Multiple Output, MIMO) in the subsequent evolution of the LTE, the number of user equipments scheduled at the same time is increased. However, an existing PDCCH limits the number of user equipments that can be scheduled by one subframe. In order to improve the capacity of the PDCCH, an enhanced PDCCH (Enhanced Physical Downlink Control Channel, E-PDCCH) is introduced. Resource scheduling is performed on the E-PDCCH in a frequency domain resource of the LTE with a resource block pair (Resource Block pair, RB pair) as a unit. Each RB pair occupies 12 subcarriers in a frequency domain and occupies one subframe in a time domain. An available resource of the E-PDCCH is a resource element (Resource Element, RE) except a PDCCH domain and resource elements that occupied by various pilot symbols (Reference Signals, RSs) in each RB pair, where the RS includes a demodulation pilot symbol (Demodulation Reference Signal, DMRS), a cell pilot signal (Cell-specific Reference Signal, CRS) and a channel state indication pilot symbol (Channel State Information-Reference Signal, CSI-RS). In an enhanced PDCCH domain, each E-PDCCH consists of an aggregated E-CCE logic element similar to a CCE. One RB pair may contain multiple E-CCE elements, where the multiple E-CCE elements may be E-CCEs belonging to one E-PDCCH and may also be E-CCEs belonging to multiple E-PDCCHs. The E-CCEs belonging to the same E-PDCCH may be transmitted by using the same antenna port (port), and the E-CCEs belonging to different E-PDCCHs needs to be transmitted by using different ports. In other words, the number of antenna ports used by an RB pair is undetermined. Due to existence of the foregoing situation, the number of ports that are actually used in each RB pair cannot be accurately determined, so the number of REs that are actually used by a DMRS cannot be determined and decoding cannot be performed. In the prior art, no matter what the number of REs that are actually occupied by the DMRS is, both a base station and a user assume that the maximum possible number of REs are occupied by the DMRS, but the manner of always assuming that the maximum possible number of REs are occupied by the DMRS results in that an RE that is not actually used by the DMRS is idle, thereby reducing the utilization of a frequency domain resource.